1. Field of the Invention
Chromatography systems perform a broad range of analysis methods to separate and/or analyze complex mixtures. There are a number of different types of chromatography systems, such as gas chromatography systems, Ion exchange chromatography systems, affinity chromatography systems, liquid chromatography systems, etc. In each type of chromatography system, components of a mixture are separated and distributed between two phases known as a mobile phase and a stationary phase.
2. Discussion of the Background Art
During operation, a mixture of various components is processed through a chromatography system at different rates. The different rates of migration through the chromatography system facilitate the separation of the mixture. Once the separation is accomplished, the different components of the mixture may be analyzed.
One conventional type of chromatography system is a High Pressure Liquid Chromatography system (HPLC). HPLC is a form of liquid chromatography used to separate compounds that are dissolved in a liquid. A conventional HPLC system is shown in FIG. 1. A reservoir 100 stores a liquid. The liquid in the reservoir 100 is considered as the mobile phase. The liquid is drawn (i.e., pumped) out of the reservoir 100 using a pump 102. A variety of pumps may be implemented, such as syringe pumps, reciprocating pumps, etc. A sample is introduced by an injector 104. The mixture of the initial liquid held in the reservoir 100 and the sample is then pushed through a column 106 packed with material. The column 106 is known in the art as the stationary phase. Different components of the mixture move through the column 106 at different rates and as a result, may be analyzed by a detector 108. Final analysis of the mixture is then performed using a computer 110. The mixture ultimately is deposited as waste 112.
A significant component of a chromatography system is the pumping system. A conventional pumping system includes at least one pump. The pump includes a chamber with a reciprocating piston disposed in the chamber. Each pump typically includes an input valve positioned at an input side of the chamber and an output valve positioned at an output side of the chamber. The input valve throttles the flow of liquid into the pump (i.e., chamber) and the outlet valve throttles the flow of liquid out of the pump (i.e., chamber). One substantial feature that distinguishes the pumping systems is whether they are low-pressure gradient pumping systems or high-pressure gradient pumping systems. In a low-pressure gradient pumping system, liquid mixing (i.e., mixing of the mobile phase if more than one solvent is used) occurs before the pump. In a high-pressure gradient pumping system, liquid mixing occurs after the liquid is processed through the pump.
Since a chromatography system separates and quantifies a sample (i.e., mixtures of compounds) based on the rate a liquid is processed through a column, controlling and managing the flow of liquid through the chromatography system is critical to performing the proper analysis of the sample (i.e., mixtures). A central component used to manage the flow of liquid through a chromatography system is the pumping system. In addition, since the liquid (i.e., flow rate, volume) that is processed through a chromatography system is extremely small, an incredible amount of precision and control must be applied to properly manage the flow of liquid through the chromatography system.
However, there are a number of problems that arise when processing liquid through the chromatography system. The problems impact the flow of liquid through the chromatography system and as a result, impact the analysis of the sample (i.e., mixtures of components). For example, varying the flow of liquid through a pump affects the analysis of the sample in a chromatography system; leaks may affect the flow of liquid through a chromatography system; incorrectly calibrated devices, such as sensor(s), may affect the flow of liquid through a chromatography system; cross over of liquids in a pumping system with multiple channels may affect the flow of liquid through a chromatography system; discontinuities in a liquid may affect the flow of liquid through a chromatography system; the intake operation of the pump may affect the flow of liquid through a chromatography system; and the piston timing of a pump may affect the flow of liquid through a chromatography system.
Thus, there is a need for a method and apparatus for managing the flow of liquids in a chromatography system. There is a need for a method and apparatus for managing the flow rate of liquids processed through a pumping system deployed in a chromatography system. There is a need for a method and apparatus for detecting and compensating for leaks within a pump. There is a need for a method and apparatus for attaining and retaining desired flow rates. There is a need for a method and apparatus for calibrating flow sensors. There is a need for a method and apparatus for avoiding channel cross over in multiple channel pumping systems. There is a need for a method and apparatus for optimizing delay volume in a pumping system. There is a need for a method and apparatus for optimizing the intake stroke in a pumping system. Lastly, there is a need for a pumping system with improved piston timing.